Chloroplast Ca2+ binding protein CAS and salicylic acid biosynthesis

Abstract

Salicylic acid (SA) is a key signal molecule in plant immunity and its synthesis is induced in response to pathogen infection. Chloroplasts are the site of SA biosynthesis; chloroplast–localized isochorismate synthase 1 (ICS1) is a key enzyme of SA biosynthesis in Arabidopsis. Furthermore it has been shown that flg22-induced SA synthesis and pathogen related 1 (PR1) gene expression are regulated by light. Recently, we demonstrated that chloroplast localized calcium binding protein CAS plays an important role in bacterially induced basal defense responses and Avr-induced hypersensitive cell death of Arabidopsis. In this study, we examined the role of CAS in flg22-induced synthesis of phytohormones. The results suggest that CAS is involved in SA biosynthesis.